3.
Monitor HO2S voltage(B1/S1) parameter on scantool
Specification : Voltage will vary from 0.1 to 0.9 V
The HO2S is used to supply the PCM with information regarding the composition of the air/fuel mixture. The HO2S is positioned in the exhaust pipe ahead of the TWC. To measure the oxygen content, the HO2S requires a supply of ambient air as a reference. The HO2S produces a voltage that varies between 0.1V and 0.9V under normal operating conditions. The Powertrain Control Module (PCM) monitors this voltage and determines if the exhaust gas is lean or rich. If the voltage input at the PCM is under approx. 0.45V the exhaust is lean, and if the voltage input is over approx. 0.45V the exhaust is rich. The PCM constantly monitors the HO2S signal during closed loop operation and compensates for a rich or lean condition by decreasing or increasing injector pulse width as necessary.
The response time of an O2 sensor can be impacted by two factors: temperature and poisoning. Poisoning of the O2 sensor is the primary failure mode of O2 sensor response time. Poisoning can come from many sources: silicone from gaskets or even in the fuel, phosphorous from engine oil, carbon from operating in a cooler environment or lead from the fuel. Most poisoning failures have the potential to clear up after the source of the poisoning has been removed. However, sometimes the poisoning may be so severe that the damage is irreversible.
Checking output signals from HO2S under detecting condition, if an output signal is out of threshold, PCM sets P0133.
Item | Detecting Condition | Possible cause | |||||
DTC Strategy | ● Determines O2 sensor functionality by checking its response rate | ● Poor connection ● Faulty HO2S ● Faulty PCM | |||||
Enable Conditions | ● 1200 ≤ Engine RPM ≤ 4300 ● 7.5g/s ≤ Air Flow ≤ 40g/s ● Engine run time 〉60sec ● Engine Coolant 〉70℃( 158 °F) ● No Decel Fuel Cut-Off Exit with Rich Bias Fueling ● No torque Fuel Reduction in effect ● No Disabling Faults ● All of the conditions above met for more than 2 sec. | ||||||
Threshold value | ● Switching counter lean to rich〈 13 ● Switching counter rich to lean〈 13 ● Response Lean Rich Transition Counter/Response Lean Rich Switch Counter 〉29 ● Response Rich Lean Transition Counter/Response Rich Lean Switch Counter 〉35 ● Response Rich Lean Average/Response Lean Rich Average〈 0.3809 ● Response Rich Lean Average/Response Lean Rich Average 〉 3 | ||||||
Diagnosis Time | ● - | ||||||
MIL On Condition | ● 2 Driving Cycles | ||||||
After warming-up, if accelerator pedal is released suddenly around 4000rpm, the HO2S signal reading will be lower than 200mV resulting from Fuel cut-off for the moment. Conversely, if suddenly accelerator pedal is depressed, HO2S signal reading will be around 0.6V ~1.0V. At idle, HO2S signal will switch from lean to rich normally.
HO2S | Response Time (70% Duty at 10Hz) | |||||
lean to rich( Less than 65ms) rich to lean(Less than 80ms) | ||||||
Connect Scantool ＆ Engine "ON"
Warm up the engine to normal operating temperature.
Monitor HO2S voltage(B1/S1) parameter on scantool
Specification : Voltage will vary from 0.1 to 0.9 V
Is the HO2S parameter displayed within specifications ?
▶ Fault is intermittent caused by poor contact in the sensor’s and/or PCM’s connector or was repaired and PCM memory was not cleared. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure
▶ Go to "Component Inspection" procedure
Visual Inspection of HO2S
Visually/physically inspect following items:
- Inspect the front HO2S for Contaminated, deteriorated or aged Front HO2S
- If contamination is evident on the HO2S, replace contaminated sensor
Is the HO2S visually / physically O.K ?
▶ Go to "Check Performance of H02S" as follows
▶ Substitute with a known - good HO2S and check for proper operation. If the problem is corrected, replace HO2S and go to "Verification of Vehicle Repair" procedure.
Check performance of HO2S
Connect scantool ＆ Engine "ON"
Warm-up the engine to normal engine temperature.
Monitor signal waveform of HO2S with scantool.
HO2S | Response Time (70% Duty at 10Hz) | |||||
lean to rich( Less than 65ms) rich to lean(Less than 80ms) | ||||||
Is the sensor signal switching properly ?
▶ Substitute with a known - good PCM and check for proper operation. If the problem is corrected, replace PCM and go to "Verification of Vehicle Repair" procedure.
▶ Substitute with a known - good HO2S and check for proper operation. If the problem is corrected, replace HO2S and go to "Verification of Vehicle Repair" procedure.
There is a memory reset function on scantool that can erase optional parts automatically detected and memorized by PCM. Before or after testing PCM on the vehicle, use this function to reuse the PCM on the others
After a repair, it is essential to verify that the fault has been corrected.
Monitor and record the Freeze Frame Data for the Diagnostic Trouble Code(DTC) which has been diagnosed.
Using a Scantool, Clear the DTCs
Operate the vehicle within conditions noted in the freeze frame data or enable conditions
Monitor that all rediness test have been verified as " Complete "
Are any DTCs present ?
▶ Go to the applicable troubleshoooting procedure.
▶ System is performing to specification at this time.
